440 PHYSOSTOMI. 



It is thus evident that blood can be purified at these respiratory air-sacs, and these fishes can be kept 

 alive hours, and even days, -without being in water, thus enabling them to traverse considerable distances 

 where aquatic respiration would be impossible. They are also able when m water, to depurate some of the blood 

 at the gills, if occasion should necessitate them to do so. ., . , „ ij_i o-t .7 



The air-vessel or swim-bladder (not respiratory air-sac) exists m two forms amongst the Silundce.. In 

 marine ones it is thick and not enclosed in bone, likewise in most of the fresh-vrater forms it is not enclosed m 

 bone, but as we approach the hills a change occurs, and in most of the genera it possesses an osseous covering. 

 The same character having been considered as valid for sub-dividing the GyprmidcB, I have deemed it not 

 inappropriate for similar employment in the Siluridce. 



OeograpUcal distribution.— Wishes of this family are very abundant in the fresh waters of India, likewise 

 in the estuaries and sea ; they are not so common however in the clear waters around the Andamans. 



TJses.—As a rule (excluding the Pseudeutropius, CalUchrous, and Ailia) these Siluroids are more eaten 

 by the poorer than the richer classes, and for two reasons, first, they are forbidden to Jews and Mahomedans,* 

 and secondly, they are very foul feeders. The Saccohrcmchus and Clarias however are deemed nourishing and 

 often prescribed for patients recovering from illnesses. The air-vessels of the marine forms are collected 

 for export to China, as they afford a, coarse isinglass. 



SYNOPSIS OF GENERA. 



A. Air-vessel not enclosed in lone, 

 a. An adipose dorsal. 



1. Macrones. Gill-openings very wide, the membranes not being confluent with the skin of the isthmus, 

 but overlapping one another, being cleft nearly to the chin. Eyes with free orbital margins. Teeth present 

 on the palate. Barbels eight. Dorsal and pectoral spines. Ventral with six, anal with from aboiit eight or 

 nine to twenty or more rays. Throughout most parts of Asia, almost invariably in fresh water. 



2. JJeiocassis. Gill-openings very wide, the membranes not being confluent with the skin of the isthmus, 

 but overlapping one another, being cleft nearly to the chin. Eyes subcutaneous. Teeth present on the palate. 

 Barbels eight. Dorsal and pectoral spines. Ventral with six, anal with from about 15 to 20 rays. Eastern 

 Bengal to the Malay Archipelago. 



3. Erethistes. Gill-openings narrow, the membranes being confluent with the skin of the isthmus. 

 Mouth narrow. Occipital, scapular, and humeral processes well developed. Eyes subcutaneous. No palatine 

 teeth. Barbels eight. Dorsal and pectoral spines present. Ventral with six, anal with about ten rays. 

 Orissa, through Bengal to Burma. 



4. Rita. GUI-openings wide, the membranes not being confluent with the skin of the isthmus, 

 and scarcely or not notched. Eyes subcutaneous. Teeth present on the palate. Barbels six or eight. 

 Strong dorsal and pectoral spines. Ventral with seven or eight rays, anal with- twelve to thirteen. 

 Throughout Sind and India (except Mysore and Madras) to Burma. 



5. Arius. Gill-openings wide, the membranes not being confluent with the skin of the isthmus, and 

 scarcely or not notched. Eyes with free oibital margins. Teeth present or absent on the palate. Barbels six. 

 Dorsal and pectoral spines. Ventral with six, anal with from about fourteen to at lea.st twenty-four rays. 

 Tropical seas. 



6. BatracocepTialus. Gill-openings wide, the membranes not confluent with the skin of the isthmus, but 

 not notched. Eyes with free orbital margins. Teeth present on the palate. Barbels two. Dorsal and 

 pectoral spines. Ventral with six, anal with about twenty rays. Seas and estuaries of India and Burma, to 

 the Malay Archipelago. 



7.- Ketengus. Gill-openings wide, the membranes not confluent with the skin of the isthmus, but not 

 notched. Eyes with free orbital margins. No teeth on the palate. Barbels six. Dorsal and pectoral spines. 

 Ventral with six, anal with about twenty rays." Andamans to the Malay Archipelago. 



8. Osteogeniosus. Gill-openings very wide, the membranes not being confluent with the skin of 

 the isthmus, but overlapping one another, being notched. Byes with free orbital margins. Teeth on the 

 palate. Barbels, one pair of semi-osseous maxillary ones. Dorsal and pectoral spines. Ventral with six, anal 

 with from about nineteen to twenty-four rays. Seas and estuaries of India to the Malay Archipelago. 



9. Pangasius. Gill-openings wide, the membranes not confluent with the skin of the isthmus, and 

 rather deeply notched. Eyes with free orbital margins. Teeth present on the palate. Barbels four. Dorsal 

 and pectoral spines. Ventral with six, anal with from about twenty-nine to thirty-nine rays. Large rivers 

 and estuaries of India and Burma to the Malay Archipelago. 



10. Pseudeutropius. Gill-openings wide, the membranes not confluent with the skin of the isthmus and 

 rather deeply notched. ,Eyes with broad adipose lids. Teeth present on the palate. Barbels eight. Dorsal 

 and pectoral spines. Ventral with six or eight rays : anal with from about twenty -seven to fifty-five rays. 

 Fresh waters of Hindustan to the Malay Archipelago. 



iT ■^™'^™S Mahomedans eating the scaleless forms in Sind I enquired the reason, observing that such were forbidden. They 

 told me however that such was not the case, as Mahomed hnUaaled fish (cut their throats to prevent the blood being eaten) and those 

 with gill-openings aire permitted to " the Faithful." 



